mm/kasan: add support for memory hotplug

KASAN doesn't happen work with memory hotplug because hotplugged memory
doesn't have any shadow memory.  So any access to hotplugged memory
would cause a crash on shadow check.

Use memory hotplug notifier to allocate and map shadow memory when the
hotplugged memory is going online and free shadow after the memory
offlined.

Link: http://lkml.kernel.org/r/20170601162338.23540-4-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/Kconfig b/mm/Kconfig
index 46ef77d5c33263f5ad05192820cd3b12c5fbd90d..48b1af447fa749c78c74217f2a09b1b1ade0fd46 100644 (file)
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -161,7 +161,6 @@ config MEMORY_HOTPLUG
        bool "Allow for memory hot-add"
        depends on SPARSEMEM || X86_64_ACPI_NUMA
        depends on ARCH_ENABLE_MEMORY_HOTPLUG
-       depends on COMPILE_TEST || !KASAN
 
 config MEMORY_HOTPLUG_SPARSE
        def_bool y

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 212bc62041de92368895e863cb98d946cca1d7f9..509974a1911e7acb73882c0c453f0ed314271db8 100644 (file)
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -737,17 +737,47 @@ void __asan_unpoison_stack_memory(const void *addr, size_t size)
 EXPORT_SYMBOL(__asan_unpoison_stack_memory);
 
 #ifdef CONFIG_MEMORY_HOTPLUG
-static int kasan_mem_notifier(struct notifier_block *nb,
+static int __meminit kasan_mem_notifier(struct notifier_block *nb,
                        unsigned long action, void *data)
 {
-       return (action == MEM_GOING_ONLINE) ? NOTIFY_BAD : NOTIFY_OK;
+       struct memory_notify *mem_data = data;
+       unsigned long nr_shadow_pages, start_kaddr, shadow_start;
+       unsigned long shadow_end, shadow_size;
+
+       nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
+       start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
+       shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
+       shadow_size = nr_shadow_pages << PAGE_SHIFT;
+       shadow_end = shadow_start + shadow_size;
+
+       if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
+               WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
+               return NOTIFY_BAD;
+
+       switch (action) {
+       case MEM_GOING_ONLINE: {
+               void *ret;
+
+               ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
+                                       shadow_end, GFP_KERNEL,
+                                       PAGE_KERNEL, VM_NO_GUARD,
+                                       pfn_to_nid(mem_data->start_pfn),
+                                       __builtin_return_address(0));
+               if (!ret)
+                       return NOTIFY_BAD;
+
+               kmemleak_ignore(ret);
+               return NOTIFY_OK;
+       }
+       case MEM_OFFLINE:
+               vfree((void *)shadow_start);
+       }
+
+       return NOTIFY_OK;
 }
 
 static int __init kasan_memhotplug_init(void)
 {
-       pr_info("WARNING: KASAN doesn't support memory hot-add\n");
-       pr_info("Memory hot-add will be disabled\n");
-
        hotplug_memory_notifier(kasan_mem_notifier, 0);
 
        return 0;